This invention relates to methods and apparatus for inspecting the appearance of substantially circular objects such as the ends of cigarettes or cigarette components such as filters.
Modern manufacturing equipment is capable of producing products at very high speeds. For example, it is not at all uncommon for modern cigarette making equipment to produce cigarettes at the rate of 5000-6000 per minute, and speeds as high as 12,000 per minute are also achievable. It is, of course, desirable to inspect the appearance of products to the greatest possible extent. Abnormal appearance in itself may be a reason for rejecting a product. Moreover, abnormal appearance may indicate an underlying structural defect which may be another reason why the product should be rejected. In addition to facilitating rejection of defective products, appearance inspection may be used to identify the types of defects that are occurring so that the production equipment can be adjusted to reduce the occurrence of such defects.
In general, the more complete the inspection of products the better. This means, for example, that, if possible, the full image of each product should be inspected, rather than just inspecting portions of each image or inspecting only presumably representative sample product images. Also, the more current the results of the inspection the better. Thus it is generally preferable to inspect products as they are being made rather than later so that when defective products are detected, corrective action can be taken promptly to minimize the production of defective products.
The foregoing considerations become more critical as production speeds increase. It becomes both more important and more difficult to completely inspect all products made at high speeds because high speed equipment tends to be more sensitive and therefore more prone to producing defects if not maintained, operated, and adjusted properly. The need for immediate warning of defects is also more critical with high speed equipment because massive quantities of defective products can be produced in just a short time if defects are not detected promptly and the equipment either stopped or adjusted to eliminate the defects.
In the case of cigarettes, various types of defects can occur in the circular or substantially circular surfaces. (Although most cigarettes are intended to be circular, some cigarettes are intended to be oval. It will be readily apparent to those skilled in the art how the principles of this invention can be adapted to oval cigarettes. Thus, because oval objects are sufficiently like circular objects for present purposes, all such objects will be referred to herein as substantially circular.) Among the defects which can occur in the substantially circular surfaces of cigarettes are (1) absence of an intended component such as a filter, (2) improper size (i.e., too large or too small), (3) improper shape (e.g., not sufficiently circular), (4) improper sealing of a wrapper (e.g., a "flag" on the "plug wrap" (the paper wrapper around a filter component) or on the "tipping paper" (the wrapper which joins the filter to the tobacco rod)), (5) a gap between the plug wrap and the underlying filter material (a so-called "by-pass") or between the tipping paper and the underlying filter plug, or (6) discoloration of the filter surface (e.g., in the case of filters made with charcoal, one or more pieces of charcoal which have escaped from their intended location inside the filter to a visible surface of the filter (i.e., so-called "black eyes")).
In view of the foregoing, it is an object of this invention to provide methods and apparatus for inspecting the appearance of substantially circular objects such as the ends of cigarettes for one or more defects of the type described above.
It is another object of this invention to provide methods and apparatus for inspecting the appearance of substantially circular objects such as the ends of cigarettes at the extremely high speeds at which such articles are typically made in modern manufacturing equipment.